1. Field of the Invention
The present invention relates to an aberration correction apparatus.
2. Description of the Related Art
At present, optical disks such as CDs and DVDs have spread and have come into general use. In addition, researches on the higher density of the optical disk have been made, and an optical disk heightened in density, such as Blu-ray Disk (hereinbelow, abbreviated to “BD”), has also been put into practical use.
In this regard, an optical pickup apparatus which plays back and records information for a plurality of sorts of optical disks with a single objective lens has been developed as an optical pickup which is installed in an optical disk apparatus. In case of coping with the plurality of sorts of optical disks with the single objective lens, even when the objective lens has been adjusted so that any aberration may not appear as to the optical disk of one sort by way of example, an aberration sometimes appears in the playback etc. of the information as to the optical disk of the other sort. Therefore, it is common to employ a configuration wherein a liquid crystal device is arranged in the optical pickup apparatus, and wherein a voltage is applied to the liquid crystal device so as to correct the aberration. In addition, regarding the liquid crystal device which is arranged for such a purpose, a type wherein regions divided concentrically are formed in both of two electrode layers included in the liquid crystal device and wherein potentials to be impressed on the respective divided regions are controlled, thereby to correct the aberration, has been introduced in large numbers in JP-A-2001-273663, and so forth.
The liquid crystal device of the above type, however, has the problem that, unless the potentials which are impressed on the respective divided regions formed in the electrode layers are appropriately controlled, the aberration correction cannot be made at a high precision.